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Abstract:

Various aspects provide for bending a bending a lead frame of a
semiconductor device package into a shape of an "L" and mounting the
package on a substrate. A horizontal portion of the bent lead-frame is
about parallel with a surface of the package. A vertical portion of the
bent lead frame is configured to extend the horizontal portion beyond the
surface of the package. A device may be mounted between the substrate and
the package.

Claims:

1. A small outline package for supporting a semiconductor, the package
comprising: a case enclosing the semiconductor; and an "L" shaped
lead-frame connected to the semiconductor and supported by the case, the
lead-frame having a horizontal portion configured for attachment to a
substrate and a vertical portion configured for providing a separation
between the case and the horizontal portion, the separation sized to
provide clearance for mounting a device under the case.

2. The small outline package of claim 1, further comprising: a substrate
attached to the small outline package; and a device mounted on the
substrate between the small outline package and the substrate.

3. The small outline package of claim 2, wherein the separation is
greater than about 0.1 mm.

4. The small outline package of claim 2, wherein the vertical portion of
the lead-frame is configured for inverting the small outline package to
mount the "L" shaped lead-frame on the substrate, and the "L" shaped
lead-frame of the inverted package has a reversed pin out.

5. The small outline package of claim 1, wherein the small outline
package is a plastic small outline package, a thin small outline package,
a shrink small outline package, or a thin shrink small outline package.

6. An electronic device comprising: an integrated circuit; a case
enclosing the integrated circuit; an "L" shaped lead in electronic
communication with the integrated circuit, a vertical portion of the lead
extending from an edge of the case about perpendicular to a first surface
of the case, a horizontal portion of the lead about parallel to the first
surface of the case; and a separation between the first surface of case
and the horizontal portion of the lead.

7. The electronic device of claim 6, further comprising a substrate
attached to the case.

8. The electronic device of claim 6, wherein the first surface of the
case is a top surface.

9. The electronic device of claim 6, wherein the separation between the
horizontal portion of the "L" shaped lead and the first surface of the
case is greater than about 0.1 mm.

10. The electronic device of claim 6, wherein the case and lead form a
small outline package.

11. The electronic device of claim 10, wherein the small outline package
is a plastic small outline package, a thin small outline package, a thin
shrink small outline package, or a shrink small outline package.

12. A method for converting a small outline package to a reformed lead
small outline package, the method comprising: bending a lead to form an
"L" shaped lead, the lead having a horizontal portion of the "L" about
parallel to a first surface of the package and a vertical portion of the
"L" shape configured to position the horizontal portion beyond the first
surface of the package.

13. The method of claim 12, further comprising mounting the reformed lead
small outline package on a substrate.

14. The method of claim 13, further comprising mounting a device between
the reformed lead small outline package and the substrate.

15. The method of claim 12, wherein the small outline package is a
plastic small outline package, a thin small outline package, a shrink
small outline package, or a shrink small outline package.

16. The method of claim 12, wherein a separation between the first
surface of the package and the horizontal portion of the "L" is greater
than about 0.3 mm.

17. The method of claim 12, wherein the first surface of the package is a
bottom surface.

18. The method of claim 12, wherein the first surface of the package is a
top surface.

19. The method of claim 18, further comprising: inverting the reformed
lead small outline package to dispose the horizontal portion of the "L"
shaped leads on a substrate, the "L" shaped leads of the inverted package
having a reversed pin out; and configuring the substrate for the reversed
pin out of the leads.

Description:

BACKGROUND

[0001] 1. Technical Field

[0002] The present invention relates to integrated circuit packaging, and
more particularly to small outline packaging for surface mount integrated
circuits.

[0003] 2. Description of Related Art

[0004] Surface mount integrated circuits can be packaged in a Small
Outline Package (SOP). An SOP includes Plastic Small Outline Package
(PSOP), Thin Small Outline Package (TSOP), Shrink Small Outline Package
(SSOP), Thin Shrink Small Outline Package (TSSOP), and Small Outline
J-Lead Package (SOJ Package). These Small Outline Packages give users
packaging choices for various types of integrated circuit and device
applications. For example, SOPs support a wide range of nonvolatile
memory component densities and features for user applications.

[0005] FIG. 1A illustrates a front elevation of a standard prior art TSOP
100. The TSOP 100 includes a case 102 and gull wing shaped lead-frame
(leads) 104. The TSOP 100 may be mounted on a substrate 106, forming a
separation 108 between the case 102 and substrate 106. A typical
separation 108 is about 0 to 0.1 mm. Unfortunately, it is difficult to
fit an additional device between the package 102 and substrate 106 due to
the limited size of the separation 108. Further, the gull wing shape of
the leads 104 provides an extension 110 from the sides of the case 102. A
typical extension 110 is about 0.8 mm. Thus, a total extension 110 on two
sides of the TSOP 100 can be about 1.6 mm or more. Such an extension 110
can result in the TSOP 100 occupying a footprint that is substantially
greater than the area of the case 102. Thus, the extension 110 of the
lead-frame 104 occupies substantial usable area on the substrate 106.

[0006]FIG. 1B illustrates a front elevation of a prior art SOJ Package
120. The SOJ Package 120 includes a case 122 and leads 124. The leads 124
are configured in the shape of a "J." Unfortunately, for similar reasons
as discussed above with respect to TSOP 100, it is difficult to fit an
additional device under the case 122. Moreover, the curved portion of the
J shaped leads 124 complicates mounting to a flat substrate.

SUMMARY

[0007] Clearance for fitting an additional device between a package and a
substrate may be provided by using an "L" shaped lead on an SOP. The "L"
shape lead has a horizontal portion about parallel to the substrate for
attachment to the substrate and a vertical portion configured for
providing a separation between a case of the package and the substrate.
An "L" shaped lead SOP may be manufactured using "L" shaped leads.
Alternatively, a standard SOP may be converted to an "L" shaped lead SOP
by reforming the leads into the shape of an "L." For example, the leads
may be bent into an "L" shape. In some embodiments, the leads are bent
upward and an inverted "L" is formed above the top of the case to make a
reverse SOP. The reverse SOP may be inverted and mounted on the
substrate. A layout of devices and traces on the substrate may be
configured for the reverse SOP while taking advantages of the decreased
footprint of the "L" shaped leads of the SOP and additional space for
devices under the "L" shaped lead SOP.

[0008] In various embodiments, a small outline package for supporting a
semiconductor is disclosed. The package comprises a case enclosing the
semiconductor and an "L" shaped lead-frame connected to the semiconductor
and supported by the case. The lead-frame has a horizontal portion
configured for attachment to a substrate and a vertical portion
configured for providing a separation between the case and the horizontal
portion. The separation may be sized to provide clearance for mounting a
device under the case. The small outline package may be attached to a
substrate and a device may be mounted on the substrate between the small
outline package and the substrate. In some embodiments, the vertical
portion of the lead-frame is configured for inverting the small outline
package to mount the "L" shaped lead-frame on the substrate, and "L"
shaped lead-frame of the inverted package has a reversed pin out.

[0009] Various aspects of an electronic device comprise an integrated
circuit enclosed in a case and an "L" shaped lead in electronic
communication with the integrated circuit. A vertical portion of the lead
extends from an edge of the case about perpendicular to a first surface
of the case and a horizontal portion of the lead is bent under the case
and is about parallel to the first surface of the case. The horizontal
portion of the lead is separated from the first surface of case. In
various embodiments, the first surface of the case is a top surface or a
bottom surface. In some embodiments, the case is attached to a substrate
and a device is attached to the substrate between the case and the
substrate.

[0010] Various embodiments of the technology include a method for
converting a small outline package to a reformed lead small outline
package, the method includes bending a lead to form an "L" shape, having
a horizontal portion of the "L" shape about parallel to a first surface
of the package and a vertical portion of the "L" shape configured to
position the horizontal portion beyond the first surface of the package.
The method further includes mounting the reformed lead small outline
package on a substrate and mounting a device between the reformed lead
small outline package and the substrate. In various embodiments, the
small outline package is a plastic small outline package, a thin small
outline package, a thin shrink small outline package, or a shrink small
outline package. The first surface of the package may be a bottom surface
of the small outline package. In some embodiments, the first surface of
the package is a top surface of the small outline package and the
reformed small outline package is inverted to dispose the "L" leads on a
substrate while the substrate is configured for a reversal of pins.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Embodiments described herein may be referenced to any one or more
of the following figures. Embodiments described herein may also be
referenced by a combination of two or more of the following figures.

[0018] FIGS. 6A-D are block diagrams illustrating exemplary steps
reforming a lead of FIG. 1 into a lead of FIG. 4.

[0019] FIG. 7A-C are block diagrams illustrating exemplary steps reforming
a lead 104 of FIG. 1 into a lead of FIG. 5.

[0020]FIG. 8 illustrates a front elevation the RSOP of FIG. 5 disposed on
the substrate.

[0021] FIG. 9 is a flow diagram of an exemplary method for converting a
small outline package to a reformed lead small outline package.

DETAILED DESCRIPTION

[0022]FIG. 2 illustrates a front elevation of an "L" shaped lead Small
Outline Package (LSOP) 200. The LSOP 200 includes "L" shaped leads 204.
The "L" shaped leads 204 include a vertical portion 206 and a horizontal
portion 208. The horizontal portion 208 is oriented about parallel with
the plane of a first surface of the case 202 for mounting on a substrate
(illustrated elsewhere herein). The horizontal portion 208 is also
oriented below a first surface 210. The orientation of the horizontal
portion 208 below the first surface 210 instead of beyond the edge of the
case 202 reduces an extension of the lead 204 beyond the edge of the case
202 to about 0 mm. The length of the vertical portion 206 provides a
separation 212 between the first surface 210 and the horizontal portion
208. The separation 212 is greater than the separation 108 of the TSOP
100 FIG. 1. The case 202 of the LSOP 200 may be based on various types of
SOP including PSOP, TSOP, SSOP, TSSOP, and the like.

[0023]FIG. 3 illustrates a front elevation view of the LSOP 200 of FIG. 2
disposed on a substrate 300, in accordance with various aspects of the
invention. A device 302 may be disposed between the substrate 300 and the
case 202. A typical separation 212 is about 0.2-0.4 mm, which is
substantially greater than a separation 108 of about 0.1 mm for a typical
TSOP, as illustrated in FIG. 1A. A separation of about 0.4 mm is
sufficient to accommodate various useful devices 302 between the case 202
and the substrate 300. In various embodiments, the device 302 includes
active components such as bare dies, Chip Scale Package (CSP), diodes,
transistors, etc. and passive components as X-tal, resistors, inductors,
and capacitors etc.

[0024]FIG. 3 also illustrates additional space available for recapture
from the extension 110 on the substrate 300 as a result of using an "L"
shaped lead 204. This leads to higher device densities. For purposes of
embodiments of the present invention, an "L" shaped lead means that the
horizontal portion 208 of the "L" shaped lead is oriented for placement
between a first surface of the case and a substrate. For example, in FIG.
3 the horizontal portion 208 of the lead 204 is between the first surface
210 of the case 202 and the substrate 300, instead of extending beyond
the footprint of the case 202. A layout and traces on the substrate 300
may be configured to accommodate the higher device densities that lead to
additional devices, including LSOP 200 devices that can be disposed in
the space recaptured from the extensions 110. Further, the layout may be
configured to accommodate devices 302 disposed between the LSOP 200 and
the substrate 300. In various embodiments, the substrate 300 includes
Printed Circuit Boards (PCB), multi-chip modules, chip-stack packages,
daughter boards, perf board, wire wrap boards, stripboard, brassboards,
hybrid integrated circuits, memory sticks, SD boards, micro SD's,
piggybacked devices, and/or the like System in package (SIP)

[0025]FIG. 4 illustrates reforming a TSOP 100 of FIG. 1A into a reformed
RLSOP 400 (RLSOP). FIG. 4 also illustrates internal components of the
TSOP 100 including a die 402, a die attach pad 416 and connectors 418.
The die 402 may be attached to the die attach pad 416 using an adhesive
before being encased in the material of the case 202. The leads 104 of
the TSOP 100 are illustrated in dotted line to illustrate their position
before being bent and reformed into the "L" shape of the leads 404,
including a vertical portion 406 and a horizontal portion 408, which are
shown in solid line in the RLSOP 400 FIG. 4. The first surface 210 of the
RLSOP 400 of FIG. 4 is a bottom surface 114 of the TSOP 100 as
illustrated in FIG. 1A. Thus, FIG. 4 illustrates bending the leads 104 to
form the vertical portion 406, which extends below the bottom surface 114
of the TSOP 100. FIG. 4 further illustrates bending the horizontal
portion 408, to be about parallel to the first surface 210 of the RLSOP
400 (underneath the bottom surface 114).

[0026]FIG. 5 illustrates reforming the TSOP 100 of FIG. 1A into a reverse
LSOP 500 (RSOP), according to aspects of the invention. "Reverse" may
refer to the horizontal portion 508 being on the side of the case 102
closest to the die 402. A dashed line 502 illustrates a horizontal plane
at about a center of the case 102. The leads 104 of the TSOP 100 are
illustrated in dotted line to illustrate their position before being bent
and reformed into the shape of the "L" leads 504, which are shown in
solid line in the RSOP 500 of FIG. 5. The first surface 210 of the RSOP
500 is a top surface 112 of the TSOP 100 as illustrated in FIG. 1A. Thus,
FIG. 5 illustrates bending the leads 104 to form the vertical portion 506
of the leads 504 of the RSOP 500; the vertical portion 506 extends above
the top surface 112 of the TSOP 100. FIG. 5 further illustrates bending
the horizontal portion 508, to be about parallel to the first surface 210
of the RSOP 500 (above the top surface 112). As illustrated in FIG. 5,
the lead-frame 104 is offset above the plane represented by dashed line
502. Thus, reforming the leads 104 into leads 504 above the top surface
112 may result in the separation 212 being greater for the RSOP 500 of
FIG. 5 than the separation 212 for the RLSOP 400 of FIG. 4 that results
from reforming the leads 104 into leads 404 below the bottom surface 114.
While the RSOP 500 and the RLSOP 400 are illustrated in FIGS. 4-5 as
being reformed by bending leads in the lead-frame, the RLSOP 400 and/or
the RSOP 500 may be formed during manufacturing (e.g., LSOP 200).

[0027]FIG. 6A-D are block diagrams illustrating exemplary steps reforming
a lead 104 of FIG. 1 into a lead 404 of FIG. 4, according to aspects of
the invention. Only one lead 104 is shown for clarity. FIG. 6A
illustrates a block diagram of typical configuration for a case 102 the
TSOP 100 of FIG. 1. In FIG. 6B, the entire lead 104 is straightened out
to the side. In FIG. 6c, the straightened lead 104 is bent straight down,
toward the bottom surface 114. In FIG. 6D, a horizontal portion 408 is
formed under the bottom surface 114. The bottom surface 114 becomes the
first surface 210 and the lead 104 of FIG. 1 becomes the lead 404 of FIG.
4. While FIGS. 6A-D illustrate various steps in reforming a lead, more,
fewer or other steps may be used to reform leads of FIG. 1 into the leads
of FIG. 4.

[0028] FIG. 7A-C are block diagrams illustrating exemplary steps reforming
a lead 104 of FIG. 1 into lead 504 of FIG. 5, according to aspects of the
invention. Only one lead 104 is shown for clarity. FIG. 7A illustrates a
block diagram of typical configuration for a case 102 the TSOP 100 of
FIG. 1. In FIG. 7B, a portion of the lead 104 is straightened out to the
side. In FIG. 7C, the straightened lead 104 is bent upward toward the top
surface 112. A vertical portion 506 is formed that extends a horizontal
portion 508 above the top surface 112. The top surface 112 becomes the
first surface 210 and the lead 104 of FIG. 1 becomes the lead 504 of FIG.
5. While FIGS. 7A-C illustrate various steps in reforming a lead, fewer,
more, or other steps may be used to reform leads of FIG. 1 into the leads
of FIG. 5.

[0029]FIG. 8 illustrates a front elevation the RSOP 500 of FIG. 5
disposed on the substrate 300, according to various aspects of the
invention. The die attach pad 416 of the RSOP 500 is positioned up, away
from the substrate, which enhances dissipation of heat away from the
device 302 and away from the substrate 300. This also reduces heating of
device 302 from the die 402 within the RSOP 500. Enhanced heat
dissipation further enhances cooling of the die 402 inside the RSOP 500.

[0030] While the reformed LSOP 400 of FIG. 4 and the RSOP of FIG. 5 are
illustrated as being reformed from the TSOP 100, a PSOP, SSOP, TSSOP,
and/or the like could be reformed into an LSOP or an RSOP. A layout of
devices and traces on the substrate 300 may be configured to accommodate
the higher device densities devices due to space recaptured from
elimination of the extensions 110. Further, the substrate 300 layout can
be configured for disposing additional devices 302 between LSOP 200,
RLSOP 400, and/or RSOP 500 devices and the substrate 300. The substrate
300 layout may be configured for the reversal of the pins from the
lead-frame 104 to the lead-frame 504 that accompanies inverting the RSOP
500. An RLSOP 400 and/or RSOP 500 that has been formed during
manufacturing rather than being reformed (e.g., LSOP 200) may be mounted
on the substrate 300. FIGS. 1-6 are not to scale.

[0031] FIG. 9 is a flow diagram illustrating an exemplary method 900 for
converting a small outline package to a reformed lead small outline
package (RSLOP). The method 900 includes a bend RLSOP lead step 910, a
mount device step 920, and a mount RSLOP step 930. The method 900 also
describes converting a small outline package to a reverse lead small
outline package (RSOP).

[0032] In the bend RSLOP step 910, a lead is bent to reform into an "L"
shape having a horizontal portion and a vertical portion. The horizontal
portion is about parallel to a first surface of the package. The vertical
portion is configured to position the horizontal portion beyond the first
surface of the package. The first surface may be a top or a bottom
surface of the original package. In various embodiments, the package is a
PSOP, TSOP, SSOP, TSSOP, and/or the like.

[0033] In the mount device step 920, a device is mounted on a substrate
such as substrate 300. The device, such as device 302 will be under the
RSLOP between the RSLOP and the substrate. In various embodiments, the
device includes active components such as bare dies, Chip Scale Package
(CSP), diodes, transistors, etc. and passive components as X-tal,
resistors, inductors, and capacitors etc.

[0034] In the mount RSLOP step, the RSLOP is mounted on the substrate. In
some embodiments, a RSOP is mounted on the substrate. The RSLOP may be
mounted over the device. When the first surface is a top surface, the
device is an RSOP that is inverted and then mounted on the substrate.
While the method 900 includes the bend RLSOP lead step 910, mount device
step 920, and mount RSLOP step 930, the method 900 may include more or
fewer steps.

[0035] As used in this specification, the terms "include," "including,"
"for example," "exemplary," "e.g.," and variations thereof, are not
intended to be terms of limitation, but rather are intended to be
followed by the words "without limitation" or by words with a similar
meaning. Definitions in this specification, and all headers, titles and
subtitles, are intended to be descriptive and illustrative with the goal
of facilitating comprehension, but are not intended to be limiting with
respect to the scope of the inventions as recited in the claims. Each
such definition is intended to also capture additional equivalent items,
technologies or terms that would be known or would become known to a
person of ordinary skill in this art as equivalent or otherwise
interchangeable with the respective item, technology or term so defined.
Unless otherwise required by the context, the verb "may" indicates a
possibility that the respective action, step or implementation may be
performed or achieved, but is not intended to establish a requirement
that such action, step or implementation must be performed or must occur,
or that the respective action, step or implementation must be performed
or achieved in the exact manner described.

[0036] The above description is illustrative and not restrictive. This
patent describes in detail various embodiments and implementations of the
present invention. The present invention is open to additional
embodiments and implementations, further modifications, and alternative
constructions. There is no intention in this patent to limit the
invention to the particular embodiments and implementations disclosed; on
the contrary, this patent is intended to cover all modifications,
equivalents and alternative embodiments and implementations that fall
within the scope of the claims. The scope of the invention should,
therefore, be determined not with reference to the above description, but
instead should be determined with reference to the appended claims along
with their full scope of equivalents.